In existing electric machines, including those with permanent magnets, magnetic interference forces contribute to undesirable energy loss, machine wear and/or interruptions to smooth operation. Electric machines, also referred to as electrical machines, include linear and rotary motors and generators. Magnetic interference forces (including torques) include forces caused by magnetic interactions that hinder, or at least do not contribute to, efficient transduction between electrical and mechanical energy, and therefore reduce the efficiency and/or smooth operation of the electric machine. The magnetic interference forces can include forces opposing the motion (e.g., cogging torque in a rotary machine) and attraction forces between moving parts (e.g., between the rotor and the stator) which can contribute to friction, stiction and forces on the bearings in the machine. For example, there can be particular positions on the path of motion of the machine's segments where magnetic interference forces, including an opposition force that acts in the opposite direction to the motion, acts to reduce the efficiency of the machine. To overcome the opposition force, additional power must be supplied to the electric machine which may be particularly problematic when starting the machine.
In existing electric machines, having permanent magnets spaced along the periphery in the rotor body in close proximity to the stator poles, may cause undesirable magnetic forces between the stator poles and the rotor. For electric machines with electromagnets, having the stator poles in close proximity to the rotor iron core may cause undesirable magnetic forces between the stator poles and the rotor body when the electromagnet is energised. In existing electric machines, embedding a magnet in a magnetic material may decrease the magnet efficiency.
Electric motors are controlled by electrical power sources and transduce electrical power into mechanical power. Existing electric motors can have inefficient control circuits and processes for providing power to the electrical coils that generate the dynamic magnetic fields, particularly at higher operating frequencies.
It is desired to address or ameliorate one or more disadvantages or limitations associated with existing electric machines, or to at least provide a useful alternative.